Lithium-ion battery and method for manufacturing lithium-ion battery

Abstract

A lithium-ion battery includes a roll formed by rolling a stack of a negative electrode plate, separator, and positive electrode plate in a rolling direction into a flattened form. A negative electrode collector portion formed at one roll end where the negative electrode mixture layer is not applied to two opposite surfaces of the negative electrode substrate layer has an undulated form. The negative electrode substrate layer has two opposite surfaces that are less the negative electrode mixture layer at the end of the roll. A positive electrode collector portion formed at the other roll end where the positive electrode mixture layer is not applied to two opposite surfaces of the positive electrode substrate layer has an undulated form. The positive electrode substrate layer has two opposite surfaces that are less the positive electrode mixture layer at the other roll end.

What is claimed is: 
     
         1 . A lithium-ion battery, comprising:
 a roll forming an electrode body, wherein:   the roll includes:
 a negative electrode plate including a negative electrode substrate layer that is a substrate of a negative electrode and a negative electrode mixture layer arranged on the negative electrode substrate layer, 
 a positive electrode plate including a positive electrode substrate layer that is a substrate of a positive electrode and a positive electrode mixture layer arranged on the positive electrode substrate layer, and 
 a separator arranged between the negative electrode plate and the positive electrode plate; 
   the roll is formed by rolling a stack of the negative electrode plate, the separator, and the positive electrode plate in a rolling direction;   the roll is pressed in a direction orthogonal to an axial direction when rolled to be shaped in a flattened form;   the roll further includes:
 a negative electrode collector portion at one end of the roll in the axial direction where the negative electrode mixture layer is not applied to two opposite surfaces of the negative electrode substrate layer, the negative electrode collector portion having an undulated form in which a thickness direction of the negative electrode substrate layer corresponds to an amplitude direction and the rolling direction corresponds to a wavelength direction, and 
 a positive electrode collector portion at the other end of the roll in the axial direction where the positive electrode mixture layer is not applied to two opposite surfaces of the positive electrode substrate layer, the positive electrode collector portion having an undulated form in which a thickness direction of the positive electrode substrate layer corresponds to an amplitude direction and the rolling direction corresponds to a wavelength direction. 
   
     
     
         2 . The lithium-ion battery according to  claim 1 , wherein:
 the undulated form is shaped to have an amplitude that decreases as the negative electrode mixture layer or the positive electrode mixture layer becomes closer; and   the undulated form is shaped to have an amplitude that increases as the negative electrode mixture layer or the positive electrode mixture layer becomes farther.   
     
     
         3 . The lithium-ion battery according to  claim 1 , wherein:
 the negative electrode collector portion and the positive electrode collector portion are connected by a connector to an external terminal of the lithium-ion battery above a flat portion of the flattened form; and   the undulated form of each of the negative electrode collector portion and the positive electrode collector portion are located downward from a lower end of the connector.   
     
     
         4 . The lithium-ion battery according to  claim 1 , wherein:
 in a flat portion of the flattened form of the negative electrode collector portion, two negative electrode substrate layers that are adjacent to each other in a thickness direction of the negative electrode substrate layer of the roll both have the undulated form so that a gap between the two negative electrode substrate layers is located at a position that varies in the thickness direction of the negative electrode substrate layer; and   in a flat portion of the flattened form of the positive electrode collector portion, two positive electrode substrate layers that are adjacent to each other in a thickness direction of the positive electrode substrate layer of the roll both have the undulated form so that a gap between the two positive electrode substrate layers is located at a position that varies in the thickness direction of the positive electrode substrate layer.   
     
     
         5 . The lithium-ion battery according to  claim 1 , wherein:
 in a flat portion of the flattened form of the negative electrode collector portion, a gap between two negative electrode substrate layers that are adjacent to each other in a thickness direction of the negative electrode substrate layer of the roll has a dimension of 18 μm or less extends at a certain location between the two negative electrode substrate layers; and   in a flat portion of the flattened form of the positive electrode collector portion, a gap between two positive electrode substrate layers that are adjacent to each other in a thickness direction of the positive electrode substrate layer of the roll has a dimension of 18 μm or less extends at a certain location between the two positive electrode substrate layers.   
     
     
         6 . A method for manufacturing a lithium-ion battery, the method comprising:
 applying a mixture layer to an electrode plate;   drying the mixture layer;   pressing the electrode plate to adjust a thickness of the electrode plate;   rolling a stack of a negative electrode plate that is the electrode plate, a separator, and a positive electrode plate that is the electrode plate to form a roll; and   flat-pressing the roll in a direction orthogonal to an axial direction in which the rolling is performed so as to press and shape the roll, wherein   the applying a mixture layer includes forming an uncoated portion where the mixture layer is not applied at one or two widthwise ends of a coated portion where the mixture layer is applied, and   the pressing the electrode plate includes setting a value of a first pressure applied to the coated portion and a value of a second pressure applied to the uncoated portion so that an elongated amount of the uncoated portion in a longitudinal direction becomes greater than an elongated amount of the coated portion in the longitudinal direction.   
     
     
         7 . The method according to  claim 6 , wherein:
 the rolling a stack includes setting tension applied to the negative electrode plate and the positive electrode plate when forming the roll so that the uncoated portion and the coated portion have the same lengths in a longitudinal direction.   
     
     
         8 . The method according to  claim 6 , wherein in the pressing the electrode plate, the value of the second pressure applied to the uncoated portion value is 1.2 times greater than the value of the first pressure applied to the coated portion.